Supplanter
by Unstoppable Cyborg
Summary: AU: While in the Darklands, Jim saw someone who shouldn't exist. Rated K-plus due to the writing style being similar to panic attacks; there are other characters but they don't feature prominently. Now includes a second chapter!
1. Chapter 1

**This is inspired by a comic by necrosishead on tumblr in which Jim finds an infant version of himself in the Darklands nursery, as well as by comments made by ch4rl13sm1th. Also, I'm not going to get into exactly _how_ Jim was able to hold a gaggletack and not get turned into his troll form in this, despite knowing that it would be a plot hole.  
**

 **I don't own _Trollhunters_ , or else I wouldn't be writing an AU fanfic based on a fancomic.**

* * *

" _You're_ the real Walter Strickler?" Jim said incredulously to the seven-hundred-year-old infant before shaking his head. He needed to find Enrique and get out of here. He didn't have a way to rescue everyone from here, at least not right now. A Trollhunter may answer every call, but he was just one person with no capacity to both fight and carry multiple infants all at the same time. He jumped to the next cradle and looked down. While the black hair indicated that this wasn't Enrique, it filled Jim with dread.

He looked down, and had to stifle a gasp since the goblins were so near.

The plaque indicated that the infant was James Lake Jr., born in the year 2000.

The plaque indicated that everything Jim had ever known was a well-constructed lie, now crumbling away like brittle stone.

* * *

"Did you always know you were a changeling?" Jim asked Nomura. Did he want to talk about it with anyone, especially her? No, but he couldn't escape if he exploded from the pressure building within his skull as he thought back to the infant whose place he had taken.

"Did you always know you were _human_ , little Gynt?" she asked with a tone of voice that implied that she was trying to sleep and if he didn't shut up soon she would find a way break out of her prison cell and permanently do the job for him.

"Well, apparently I'm not," he admitted, because if the world already wanted him dead, then he may as well be true to himself.

The two cells were silent before Nomura let out an exasperated sigh. "Did I ever tell you how I first met Draal?"

* * *

"And then the council was, like, thinking that you were a changeling or something and let's face it, that's crazy, you've held a gaggletack and defeated Bular when he tried to open the bridge in the first place!" Toby said as he, Jim, and Claire walked home from the forest where Killahead Bridge had stood less than an hour ago. "Of course, that's when we got thrown out even though Vendel was making the argument that you're not a changeling because duh!"

Jim chuckled in a way that sounded like he was trying to get himself to cry and was too dehydrated to do so.

"You okay, Jimbo?" Toby asked as Claire put a comforting hand on his shoulder.

'When I was in the Darklands," Jim started, and had to swallow the rising panic in his throat. "I saw someone that shouldn't exist. I saw an infant version of me."

Claire and Toby stopped walking, and Jim squeezed his eyes in anticipation. They would hate him, if not for being a changeling in the first place then for leaving the baby version of him - _no_ , the _real_ James Lake Jr., back in the Darklands.

"Are... are you sure?" Claire asked. Jim opened his eyes but didn't look directly at their faces. It would make him seem like a liar, but that was what he had always been.

"He looked just like _I_ did in the baby photos my mom has of me. Well, I guess of him, unless they're from around the same time he was kidnapped." Claire took her hand off of his shoulder.

"Did... did you know?" Toby asked, sounding torn between wanting to comfort his best friend and wanting to fight the person who had apparently lied to him his entire life.

"Of course not!" He was hyperventilating now. "Tobes, I was just as surprised as you were when I found out that trolls exist!" He backed away from them. They _hated_ him, they _had to_ hate him, they didn't _believe_ him, they wouldn't _ever_ believe him, they would just kill him and give the amulet to someone who _deserved_ it, they thought he was a failure _and-_

Two pairs of arms encircled Jim, and he tried not to scream because he _couldn't_ let his will break and let them take him _and-_

"It's okay, we believe you," Claire said as Toby rubbed his back.

"I wouldn't tell Vendel if I were you, though," Toby said. "Team Trollhunters is _already_ on thin ice with the tribunal."

* * *

NotEnrique started laughing when Jim finished his story.

"I'm telling you, I really saw him!" Jim told him.

"You real- you really think that _you_ could be a changeling after you chased me around with a _gaggletack?_ Yer mum's a doctor, right? Maybe instead of coming to me, you should go get yer head checked!"

"I _know_ what I saw."

"You sure that wasn't some _other_ kid with your name and year of birth?"

"If I had any doubt, I wouldn't have told _anyone_. Claire said you were able to use a mirror to show her Enrique. Show me how."

"For what?"

Jim reached into his backpack and took out a pair of stiff socks.

"Jeez, kid! Why didn't you lead with that instead of the sob story? Eh, whatever," NotEnrique said as he snatched the socks out of Jim's outstretched hand. "But seriously, _why_ do you want to be able to see the baby so much?"

"I'm not going to just disappear on my - on Dr. Lake for no reason," Jim said, and NotEnrique rolled his eyes at the irony in the fact that Jim had technically done just that when he had gone traipsing into the Darklands. "And it's going to be shocking enough when she finds an infant and me in whatever I'm _supposed_ to look like. After I defeat Gunmar, I'll need to show her proof before I go rescue the _real_ Jim."

"Are you _really_ planning on rescuing all those babies?"

"Yeah, why wouldn't I?"

"Well, there's a lot of people who would suddenly be revealed to the rest of the world. I mean, it was pretty fine for me, since Claire already knew and I didn't have time to get attached, but what about the changelings who _aren't_ babies? Tons of people will be exposed as trolls, with nothing but infants in their place."

Jim looked away, not wanting to think about it. "I get what you're saying, but I can't just leave them in the Darklands, though."

* * *

"And _where_ do you think _you're_ going?" Barbara asked Jim as she caught him trying to sneak out the door. In actuality, he was going to go train at the Hero's Forge, but he couldn't tell her that. He had promised her once that he'd tell her everything that was going on, and one day he was going to keep his promise. He wasn't nearly ready for that particular day today, though. He didn't know if he'd ever be ready to face the Darklands again, but he'd have to.

"Um, I was going to help Claire with, um, homework!" Jim said as she grabbed his shoulders. He tried not to panic because as of now, she had no reason to want to hurt him. No reason at all. It wasn't like she _knew_ that he had stolen her son and -

"You have a phone and a computer, you can contact her with those," Barbara said as she marched him up the stairs. "I know that things have been hard for you -" _\- and her holding him that way was making them harder -_ "- but this behavior has to stop." They neared the bathroom. "I want to trust you, but you need to _tell_ me things. As your mother -"

"You're not," Jim blurted out; he immediately regretted it. It had been so nice, pretending that everything was fine.

Dr. Lake paused. "What did you say?" Her grip tightened on his shoulders.

Jim wrestled out of her grip and spat on the mirror. "I'm not your son. I've lived just about my entire life here, but I'm not your son." His familiar appeared in the mirror. "He is." As Dr. Lake stared at her _real_ son, Jim pushed past her and ran down the stairs and out the door.

* * *

Jim didn't go to Trollmarket. He didn't go because the tribunal had been so close to the truth when they accused him of being a changeling working for Gunmar. He didn't go because they had been true for half of it, and in all honesty why would he even exist if it wasn't for the glory of Gunmar? It had been something he could ignore when he could still pretend to be human, pretend that everything was fine, but he had had to go and ruin it. He couldn't have just have gone along with being grounded and called for Claire to open a portal for him?

He was tired. He was tired of lying, tired of fighting, and definitely tired of walking for hours without any true purpose. He had turned his phone off after it had been going off every several seconds. He didn't want to see the texts from his friends, who were probably wondering where he was. He didn't want to see the texts from his _\- from Dr. Lake_ , who probably wanted to know where her _real_ son was.

"Jim?" a voice called. "Jim!" And now she was here.

Jim backed away. "I'm sorry, I didn't want to tell you like this, I didn't know that I replaced him until recently -"

She placed a hand on his shoulder. Jim doubted that being this close to hyperventilating was the intention of Rule Number One, but he was certainly afraid.

"I was able to rescue Claire's brother, just give me some time and I'll go back and get your real -"

She pressed him into a hug, stroking her fingers through his hair. "You're my real son. You're apparently adopted, but I raised you. You're my son. Let's go home, and talk about everything that's been going on for... for however long this has been going on."


	2. Chapter 2

**So I originally wasn't going to write a second chapter, but then I started thinking about why Jim would be immune to gaggletacks and also not remember that he's a changeling. Originally, I had wanted to publish this _before_ Season 3, but given the way said season turned out I tweaked parts of the chapter so it wouldn't be as sad... hopefully.**

 **Naturally, I don't own Trollhunters.**

* * *

"You can't balance both worlds! Eventually you'll have to pick a side!" the version of Jim in the green jacket said as he struggled against the others. Given what he said, Jim was surprised by how human he looked. Not even the part of him that was fully immersed in the world of trolls could actually do what he said for the real Jim to do.

"Are you sure about that? We're a changeling. Existing within both worlds is what we do," Jim said to himself.

The other Jim glared. "Oh, really? Then why do you still only seem to be human, with nothing but our familiar as proof? If I take over, Dr. Lake will have her son back and Trollmarket will have a _real_ Trollhunter."

"No. We're stronger together," Jim said before absorbing the clones back into the amulet.

Jim bit his lip. He was certainly glad that none of the versions of him had had horns, slitted eyes, or anything else of the sort. Not only would that have been difficult to explain to Claire's parents and the teachers, but even though he was a changeling he was very fine with not having physical evidence of it other than his ability to talk to goblins and his familiar.

* * *

"We're all here because I made a mistake, and I'm going to continue to make mistakes. But saving an innocent life isn't one of them. When I was in the Darklands, I realized just how many kids never got to grow up, and I decided that I would make the same choice as many times as it took too-"

"He admits to it! He'd do the same thing and doom us all over again!"

That was not what Jim had been going for.

* * *

Jim had honestly expected his worst fear to have been Gunmar, or the corpses of his family and friends like when pixies attacked, or maybe a resurrected Bular or Angor Rot. Himself in the Eclipse Armor? That wasn't something he was expecting.

Well, he had fought himself before, when he had gone to the Nuñez barbeque. This shouldn't be too hard.

Heading into the Darklands alone shouldn't have been too hard, either.

When he got a good look at the doppelganger, he realized why he was his own greatest fear. Not the James Lake Jr. who was still cooing within the Darklands, but the changeling who had been created to bring about the end of everything he had come to hold dear. It hadn't just been Merlin's amulet that was ruining his life, but it wasn't like it had been his own to begin with. Even though Toby, Claire, Blinky, AAARRRGGHH!, and his mom had ended up not caring about his origins, it was still felt like fragile acceptance. Would they accept the snarling figure in armor? Even as he stared into what were almost certainly his own slitted eyes, Jim knew had had an easier time accepting that he had replaced an infant. Maybe that was because he hadn't ever seen his true form until now, not even when he held a gaggletack. But why?

"You... you're a part of me," Jim said, and the doppelganger paused. "You're a part of me, and I need to accept that. All of it."

* * *

"Mom? I'm home!" Jim said. While evacuating Trollmarket, he had sent her a quick text, stating that despite the message Toby had given not even an hour earlier, he was alive and very much not in the Deep.

"Hello, Young Atlas," Mr. Strickler said. Jim's fingers ghosted over the Amulet upon hearing the other changeling's voice.

"Mr. Strickler?" What was he doing here?

"After everything that's come to light, I believe Ms. Nomura and I can offer you some assistance." As if on cue, she walked out from behind the wall separating the dining area from the kitchen. Jim's hands returned to his sides; he trusted her more than he did his former principal and perhaps once-again teacher, even if she was holding a tea cup.

"I'm guessing Nomura has filled you in?" Jim asked, but the door opened before he could answer.

"Jim, are you - oh," his mom said as she took in the sight of the three of them.

"They're not here to kill me," Jim clarified as she reached towards her purse, likely to pull out her pepper spray.

"Then why?" she asked, glaring at the other two adults in the room.

"How much has he told you?" Nomura asked, being the less phased of the duo.

"That the two of you have tried to kill him multiple times," his mom said as she tried to discreetly ready a guard position from Krav Maga. While she was certainly a force to be reckoned by humans, Jim doubted she could win against either of the other changelings in the room. He placed himself between them.

"Nomura also saved my life in the Darklands, and Mr. Strickler, well, he said they're here to help."

"Barbara, we -" Mr. Strickler started, only to be pinned down by a glare.

"Don't call me Barbara."

"Of course, Dr. Lake," he said with a surprising amount of sheepishness. "My associate -" Nomura rolled her eyes at the title "- and I are hear to help Jim stop Gunmar, as well as provide some information for as to what he is."

"Or at least, we're going to assume it's about Little Gynt here and not some other changeling who came into the world about sixteen years ago," Nomura said, gesturing For. "It should be him, though, since the records we found at the Janus Order indicated there had only been one who had survived at. Then again, it was a mess there, with all the bodies; I wouldn't be surprised if Gunmar destroyed some of the files out of spite."

"Wait, how long ago did you return to the Janus Order?" Jim asked.

"About two hours ago," Mr. Strickler said. "Thankfully Gunmar and his soldiers were gone, or the chances of us reaching out to you would be lessened."

"We must have just missed you, then," Jim said.

"What did you find on Jim?" Dr. Lake asked, and he tried not to flinch, tried not to spiral into wondering if she was thinking about him or if she was thinking about her real, human son still trapped in the Darklands.

"About twenty years ago, experimentation was started on thirty-or-so newly-captured troll whelps at the orders of our creator, the Pale Lady," Mr. Strickler said. "The goal was to take away a Changeling's main weakness - the Gaggletack."

Nomura rolled her eyes. "What Avocado here means is the fact that we're forced to change forms when we come into contact with them. It'd be easier than trying to eradicate iron horseshoes." Mr. Strickler glared at her and made a move to take back the conversation, but she continued talking over him. "Only one of the whelps survived the process, and was replaced in a family in New York. That particular whelp only grew more ill, and disappeared quite suddenly. We assumed it died, but, well, sixteen years later we have a seemingly-human Trollhunter who can carry around a Gaggletack but also has a human familiar in the Darklands."

Barbara gazed at her son, a sad realization dawning in her eyes. "You got so sick at the end of our trip to visit my parents when you were a baby, but I, well, your dad and I had thought it had been the weather or something."

"Mom, it's okay, you couldn't have known," Jim said before frowning. "Could me getting sick be why I don't remember working for Gunmar or..." Or how to become what he had seen in the Deep.

"That is possible," Mr. Strickler said. "According to our records you were also very young to be sent out, so that could also play a part. The fact that he seems to hold a deeper bond with his familiar than the rest of us could also be a reason."

Taking in the quizzical expressions from the mother and son Nomura continued. "Since I was on the same plane of existence as my familiar when I was trapped in the Darklands, I couldn't turn into my human form even if I wanted to. NotEnrique is now nothing more than a tiny troll with an immunity to sunlight since you rescued Claire's brother. If I'm remembering your complaining correctly from the cells, you didn't realize that you weren't human until after you had been in the Darklands for two weeks."

"Looks like you're going to have to still try and graduate from high school, then," Barbara said. Jim groaned, remembering the conversation they had had. His grades and excessive tardiness were starting to really starting to cut into his ability to pass his sophomore year, and he had argued that once he got his familiar back from the Darklands, he couldn't hope to live a normal human life.

"Now, Young Atlas, do you have a gaggletack available?" Mr. Strickler asked. Jim pulled the cloth-wrapped horseshoe out of his bag and set it on the table.

"Just in case the immunity wears off," Jim said as the questioning gazes of the adult changelings burned into him.

"Since it forces the rest of us into our other forms, you might be able to use it to jump-start your transformation," Nomura said. "Try grabbing on to it and summoning your other form." Mr. Strickler looked on between the other two changelings in the room with what almost seemed to be boredom until he realized that Barbara was still glaring at him.

Jim unwrapped the gaggletack, but hesitated to do any more of what he had been told.

"It's okay, Jim," his mom said. "I'm not going to reject you just because you have horns, stone for skin, or anything else."

"You're certainly a better parent than most of us get," Nomura said as Jim grabbed onto the gaggletack. "He's lucky to have you."

A minute passed, and then another. Jim tried to ignore Mr. Strickler's gaze and his mom and Nomura's conversation. He needed to accept the form of himself that he had encountered in the Deep. He would only be stronger if all the parts of him were working together.

It was easier said than done, but he was trying.

"Yeah, about that immunity," Jim said. "I don't think it's going to wear off any time soon."

"I told you we should have brought the Grave Sand," Mr. Strickler said to Nomura.

"What's Grave Sand?" Jim asked.

"It's the ground up bones of fallen Gumm-Gumms. We changelings use it to help cast aside our human forms and unlock our more Trollish nature."

"How does it work?"

"One breathes it in, preferably through the nose. If eaten, the effects are more difficult to handle."

As someone who was in over her head, she knew that it was probably a good idea to listen to any option that could help her son survive, even if it was coming from her ex. As a doctor, Barbara Lake knew that the various chemicals one put in one's body could do either help or harm, but generally if they were to be inhaled through the nose they had a tendency to do harm.

"You're not going to be having my son snort a stimulant!"

"And to think you used to teach teenagers," Nomura said, clearly enjoying this too much.


End file.
